The present application is based on Japanese Priority Document 2000-270927 filed on Sep. 7, 2000, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a platen supporting device for supporting a platen of a printer.
2. Discussion of the Background
As a platen of a printer, not only a platen called platen roller having a paper feed function, but also a flat platen not having a paper feed function is known. In such a platen, both ends thereof are fixed to platen supporting members such as frames opposed to each other. A more concrete description will be given below with reference to FIGS. 7 and 8, of which FIG. 7 is an exploded perspective view showing a part of a platen supporting structure and FIG. 8 is a side view thereof.
A platen 15 is a flat type and is disposed in opposition to a wire dot head 20. Mounting holes 15a are formed in both longitudinal ends of the platen 15. Mounting screws 26 are inserted respectively through the mounting holes 15a and are threadedly engaged with platen supporting members 25 formed in frames 24 for example, whereby the platen 15 is fixed.
In the printer, however, there occurs noise during conveyance of paper, during movement of a carriage with the wire dot head 20 mounted thereon, or when the wire dot head 20 is driven during movement of the carriage. Particularly, in case of using an impact type wire dot head 20, the platen 15 is a loudest noise generation source because it is struck by the wire dot head 20.
As shown in FIGS. 7 and 8, in the case where the platen 15 is mounted directly to the platen supporting members 25, vibrations of the platen 15 are transmitted to the platen supporting members 25. The vibrations are propagated to the frames 24 and are amplified thereby, thus generating a loud printing noise. For damping this noise there has been adopted, for example, a measure of affixing a sound absorbing material to an inner surface of a case of the printer. However, a further anti-noise measure is demanded because the striking sound of the wire dot head 20 is very high.
Moreover, in the case of a flat platen 15, the surface of the platen 15 opposed to the tip of the wire dot head 20 is sometimes not parallel to the head tip. More particularly, for example if paper is conveyed from left to right in FIG. 8 and if a gap between the wire dot head 20 and the print head 15 on an upstream side in the paper conveying direction is a and that on a downstream side is b, the a and b are sometimes not equal to each other. In this case, there occurs a difference in print density between the upstream side and the downstream side, with consequent deterioration of the print quality. To eliminate such a difference there has been developed a mechanism for adjusting an inclination of the platen 15, but the structure of the mechanism and the adjusting work are complicated.
In certain embodiment, there is a platen having an impact absorbing element, it possible to damp a printing noise quickly in its generation source.
According to embodiment of the present invention, a platen having a surface opposed to a print head is fixed to a platen supporting member by a fixing member. In this case, a first impact absorbing member is interposed elastically between the platen and the platen supporting member. With a vibration absorbing action of the impact absorbing member, it is possible to prevent propagation of vibration between the platen and the platen supporting member.